Cleaning method

ABSTRACT

This invention relates to a method of softening water and/or in which the deposition of hard water scale is inhibited. The invention relates in particular to such a method carried out in a domestic environment, in particular in ware-washing machines. In particular the method relates to the softening of water after the main wash of a ware-washing machine, in particular in the rinse cycle of a ware-washing machine. The invention also relates to water-softening compositions for such methods.

This application is a 371 national phase application of PCT/GB03/00546(now WO 03/080918), filed on 7 Feb. 2003.

This invention relates to a method of softening water and/or in whichthe deposition of hard water scale is inhibited. The invention relatesin particular to such a method carried out in a domestic environment, inparticular in ware washing machines. In particular the method relates tothe softening of water after the main wash of a ware washing machine.The invention also relates to water-softening compositions for suchmethods.

It is well known that certain metal compounds, notably calciumcompounds, when present in water, have a significant effect on theproperties of the water. For example, “hard” water containing asignificant loading of soluble calcium and magnesium compounds mayrequire a large amount of soap or detergent in order to form a lather.Scale deposits can readily form from such water, for example on heatingor pH change or evaporation. These can be incrustations, which are lefton a surface that has come into contact with the hard water. Particularissues arise in ware washing machines, such as dish and clothes washingmachines. In particular incrustations and watermarks may be left on thesurfaces of the machines as well as the items washed therein. Inparticular issues arise with incrustation of heating elements, whichreduced their life span and efficiency. A further issue arises in thatwater marks may be left on the hard surfaces of items washed in the dishwasher and in fact incrustation can be found on the surface of clotheswashed in the clothes washing machines which are perceptible to thewearer as feeling harsh to the touch.

There have been many proposals for removal of metal ions from aqueoussolutions. In the industrial context proposals have included filter bedsand polymeric filters for capturing heavy metal ions from an aqueoussolution flowing within a passageway. Examples are given in EP992238Aand GB20869564A. In the domestic context chelating compositions can beadded to an aqueous washing solution and these can capture metal ions,such as calcium ions. Examples of chelating compositions are given inEP892040A.

Typically in clothes washing machines cleaning compositions are providedwhich are “built” which provide a water softening effect and an increasein the performance of the detergent. In addition products can be used(such as sold under the brand name Calgon in Europe) which are added ontop of cleaning compositions which have a water softening effect.However, such compositions are not effective for softening the water inthe rinse cycle of clothes washing machines since such compositions arepumped out of the machine along with the dirty water prior to the rinsecycle.

We have found that by providing a water-softening agent to the rinsecycle of a clothes washing machine significant benefits can be found,such as reduction in the amount of incrustation and/or water marks. Inaddition we have found benefits on the softness of the fabrics after thewash, a reduction in the degree of shrinkage of the fabrics and areduction in the amount of wrinkles found on the fabrics after the wash.In addition we have found that traces of the detergent from the mainwash are better removed from the fabric in the rinse cycle by theaddition of a water-softening active in the rinse cycle of the clotheswashing machine.

Therefore, we present as a feature of the invention a method ofsoftening the water in the rinse cycle of a clothes washing machine, byproviding a water-softening agent to the water of the rinse cycle of theclothes washing machine.

We present as a further feature of the invention a method of reducingthe shrinkage of fabric (preferably natural fibres such as cotton, woolor silk) after a wash of the fabric in a clothes washing machine,comprising adding to the water in the rinse cycle of the clothes washingmachine a water-softening agent.

We present as a further feature of the invention a method of reducingthe amount of wrinkles present in a fabric after a wash of the fabric ina clothes washing machine comprising adding to the water in the rinsecycle of the clothes washing machine a water-softening agent.

We present as a further feature of the invention a method of assistingthe removal of detergent cleaning composition residue present in afabric after a wash of the fabric in a clothes washing machinecomprising adding to the water in the rinse cycle of the clothes washingmachine a water-softening agent.

Preferably the water-softening agent is present in a composition, whichcomposition is substantially free from any surfactant, and/or bleach.

A further feature of the invention is a rinse additive compositioncomprising:

-   -   a) 5 to 90% (preferably 5to 20%) by weight of at least one        water-softening agent, and    -   b) 0 to 90% (preferably 40 to 90%) by weight of water.    -   A further feature of the invention is a rinse additive        consisting of, or consisting essentially of:    -   a) 5 to 90% (preferably 5 to 10%) by weight of at least one        water-softening agent,    -   b) 0 to 90% (preferably 40 to 90%) by weight of water, and    -   c) 0 to 20% (preferably up to 15%) by weight of at least one        ingredient selected from; perfume, pH adjusting agent (an acid        and/or a base), pH buffer and preservative.

A further feature of the invention is a kit of parts comprising

-   -   a) a rinse additive composition, as described herein, and    -   b) instructions for the user of the product to add the rinse        additive to the rinse cycle of a clothes washing machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) and 1(b)—depicts the effect of various detergents on cottonswatches.

A number of different techniques can be envisaged for the delivery of awater-softening agent to a clothes washing machine during the rinsecycle.

A simple technique can be used in a clothes washing machine where thewater-softening agent is added into the dispensing drawer, usuallyreserved for the fabric conditioner. Alternatively a “rinse hold” cycleis selected on the clothes washing machine, found on most machines sothat the user may add bleach to the rinse cycle, and the water-softeningagent is added directly to the water of the rinse cycle, optionally inaddition to a bleaching composition.

A more sophisticated technique would be to provide sustained release ofthe water-softening active through the wash and rinse cycle in a singleproduct. Delayed release of the water-softening agent could be used suchthat the agent is released during the rinse cycle only, or substantiallymost of the composition (greater than 50%) is released into the rinsecycle.

Delayed or sustained release can be achieved in several ways.

Increasingly popular is the delivery of cleaning and water-softeningcompositions as compressed compositions, typically a tablet. These areconvenient, providing a unit dosage which is easily handled.

Multi-region compressed compositions are now of interest in being ableto provide such advantages as sustained release of active(s), or delayedrelease of active(s) from one or more separate region of a compressedcomposition. Delayed or sustained release can be achieved by pressingeach region with different forces or selecting different ingredients,such as adding disintegrants, to produce dissolution of each region atdifferent times during the wash and/or the rinse cycle.

It is a preferred feature of the invention that there is providedwater-softening active(s) during the wash and the rinse cycle. This maybe provided by a single composition that releases active during bothcycles or two distinct compositions which are used independently foreach cycle.

Therefore, we present as a feature of the invention a kit of partscomprising

-   -   1) a first composition comprising at least one water-softening        active;    -   2) a second composition comprising at least one water-softening        active; and    -   3) instructions for the user of the product to add the first        composition to the wash cycle of a clothes washing machine and        to add the second composition to the rinse cycle of a clothes        washing machine.

The first and second composition may be in the form of a single item(such as a multi-region tablet or a dual chambered bottle) or twoseparate items (such as a tablet and a liquid).

Preferred product formats are:

1. Liquid

-   -   a. A water softening liquid composition in a liquid dispensing        container. In use the water softening liquid composition is        dispensed into the rinse cycle of the clothes washing machine or        the same composition is added into the main wash and rinse cycle        of the washing machine.    -   b. Two water softening liquid compositions. In use one        composition is added to the main wash and the second composition        is added to the rinse. The two liquid compositions are either        held in two separate liquid dispensing containers or a single        double chambered liquid dispensing container.        2. Solid    -   A water softening solid composition, presented as a powder,        granulate or tablet. In use either the composition is added to        the rinse cycle of the clothes washing machine or the same        composition is added to the main wash and the rinse cycle of the        clothes washing machine. Alternatively different solid        compositions are dispensed into the main wash and the rinse        cycle of the clothes washing machine.

Preferred amounts of water softening agent are from 2 to 40% by weight,ideally 5 to 20% by weight. There are three main types of method ofaction for water-softening agents, described below.

1) Ion exchange agents—such agents include alkali metal (preferablysodium) aluminosilicates either crystalline, amorphous or a mixture ofthe two. Such aluminosilicates generally have a calcium ion exchangecapacity of at least 50 mg CaO per gram of aluminosilicate, comply witha general formula:0.8-1.5 Na₂O.Al₂O₃.0.8-6 SiO₂and incorporate some water. Preferred sodium aluminosilicates within theabove formula contain 1.5-3.0 SiO₂ units. Both amorphous and crystallinealuminosilicates can be prepared by reaction between sodium silicate andsodium aluminate, as amply described in the literature.

Suitable crystalline sodium aluminosilicate ion-exchange detergencybuilders are described, for example, in GB 1429143 (Procter & Gamble).The preferred sodium aluminosilicates of this type are the well knowncommercially available zeolites A and X, and mixtures thereof. Also ofinterest is zeolite P described in EP 384070 (Unilever).

Another class of compounds are the layered sodium silicate builders,such as are disclosed in U.S. Pat. No. 4,464,839 and U.S. Pat. No.4,820,439 and also referred to in EP-A-551375.

These materials are defined in U.S. Pat. No. 4,820,439 as beingcrystalline layered, sodium silicate of the general formulaNaMSi_(x)O_(2x+1).YH₂Owherein

M denotes sodium or hydrogen,

x is from 1.9 to 4 and y is from 0 to 20.

Quoted literature references describing the preparation of suchmaterials include Glastechn. Ber. 37,194-200 (1964), Zeitschrift fürKristallogr. 129, 396-404 (1969), Bull. Soc. Franc. Min. Crist., 95,371-382 (1972) and Amer. Mineral, 62, 763-771 (1977). These is materialsalso function to remove calcium and magnesium ions from water, alsocovered are salts of zinc which have also been shown to be effectivewater softening agents.

2) Ion capture agents—agents which prevent metal ions from forminginsoluble salts or reacting with surfactants, such as polyphosphate,monomeric polycarboxylates, such as citric acid or salts thereof,polycarboxylate polymers, such as polyacrylates, acrylic/maleiccopolymers, and acrylic phosphonates, EDTA, algins, alginates.Heptonates/glucoheptonates and gluconates are especially preferred.

3) Anti-nucleating agents—agents that prevent seed crystal growth, suchas polycarboxylate polymers, such as polyacrylates, acrylic/maleiccopolymers, and acrylic phosphonates, and sulfonates. Such polymers mayalso act as ion capture agents as well. Phosphonates and nonionic polycarboxylates, such as citrates, are especially preferred.

Preferred water softening agents are water-soluble and include thefollowing polycarboxylate polymers, such as polyacrylates,acrylic/maleic copolymers, and acrylic phosphonates; monomericpolycarboxylates such as citrates; heptonates; glucoheptonates;gluconates; oxydisuccinates; glycerol mono- di- and trisuccinates;carboxymethyloxysuccinates; carboxymethyloxymalonates; dipicolinates;hydroxyethyliminodiacetates; phosphonates; iminodisuccinates;polyaspartic acids; BHT; phosphonate stabilisers such as,diethylenetriaminepenta (methylene phosphonic acid and its correspondingpentasodium salt available under the trade names Dequest 2060 andDequest 2066 Monsanto Chemical Co), DTPMP and DTPMA (Dequest 2010) andHEDP.

Preferably the water-soluble water softening agent is a neutralised orpartially neutralised carboxylic acid, such as citric acid, succinicacid or maleic acid, and/or a neutralised or partially neutralisedpolycarboxylic acid, such as a polyacrylate of Mw: 4000-8000 (such asAcusol 445N (Rohm & Haas) CAS REG Nr. 66019-18-9 or Sokalan from BASF)and/or gluconates or polyaspartates or heptonates (such as Crodaquestseries by Croda).

The invention will now be described, by way of embodiment, withreference to the following examples.

Liquid Composition

A non-thickened aqueous solution containing, as actives, 5 to 60% byweight of a citrate/ citric acid mixture and 5 to 60% by weight ofsodium heptonate. This solution can be dosed in equal amounts (10 to 100ml, ideally 10 to 70 ml) in the main wash, with a wash detergent, and inthe fabric softener compartment. A perfume is a preferred additionalingredient in the composition. Additional water-softening actives whichmay be added are 0.1 to 20% by weight of a phosphate, polyphosphonate ora mixture thereof.

Solid Composition

A powder containing, as actives, 5 to 60% by weight of a citrate/citricacid mixture, 5 to 60% by weight of sodium heptonate, and, optionally,0.1 to 20% by weight of a phosphate, polyphosphonate or a mixturethereof.

Dual Chamber Bottle

Two water softening liquid compositions in the format of a dual chamberbottle (or two bottles attached or packaged together).

-   -   One chamber/bottle with a concentrated water-softening        composition as a thick gel, dosed together with a wash detergent        in the main wash, dosing of 10 to 100 ml, ideally 10 to 70 ml.        The gel is a pure liquid polyacrylate, such as one of the        products under the Acusol brand (Rohm & Haas). These polymers        are available as a thick water solution (usually 40-50% by        weight). The water softening agent being 10 to 30% by weight of        a homo or co polymer of polyacrylic acid neutralised (completely        or partially) with an inorganic base and 5 to 20% by weight of        citric acid neutralised (completely or partially) with an        inorganic base. The remaining part of the composition being,        optionally, further ingredients, such as perfume, dye etc.    -   The second chamber/bottle has a non-thickened aqueous solution        containing, as an active, 5 to 60% by weight of a citrate/citric        acid mixture. It must be dosed in the fabric softener        compartment. A perfume is a preferred additional ingredient in        the composition.

Additional actives which may be added are 0.1 to 20% by weight of aphosphate, polyphosphonate or a mixture thereof.

Rinse Additive

The citrate formula described above in the second chamber/bottle may beused as a rinse additive.

Results

(a) Incrustation on heating elements and fabric (Wrinkle Test)

Standard cotton swatches (WFK 10A) were washed with (a) detergent alone(Dash Essential-Italy) and (b) detergent +16 ml of a water softeningcomposition (100% Acusol 445, which is a 48% water solution ofpolyacrylic acid partially neutralised) added to the main wash and 35 mlof a water-softening composition (9% citric acid/31.2% trisodium citratebihydrated/59.8% water) added to the rinse cycle of a Siemens Siwamat5020 machine set at 60° C. and washed 24 times with a set water hardnessof 43° fH.

Dash ® Essential Dash ® Dash ® Detergent (a) Essential Essential (b)(dosage) 236 g 236 g 168 g Additive (*) Acusol ® in Main Wash (16 ml)and citrate/citric solution (35 ml) in last rinse Heating 1010 90 30Element Incr. (mg) Laundry 11.35 1.05 2.95 ash % at 550° C. Empa 221Laundry 9.52 1.34 1.33 ash % at 550° C. Wfk 10A Laundry 6.1 0.6 0.79 ash% at 550° C. Honey CombMain Wash and Rinse with 43° fH. hardness water except (*) where therinse cycle was with deionised water.Wrinkle Test

The cotton swatches tested above were analysed for the presence ofwrinkles. The results are shown at FIG. 1.

1. A method of softening the water in the rinse cycle of a clotheswashing machine by providing an acidic water-softening composition whichis a liquid or a solid selected from a powder, granulate or tablet andconsists of (a) 5 to 90% by weight of at least one water-softeningagent, (b) 0 to 90% by weight water, and (c) up to 20% by weight of atleast one ingredient selected from the group consisting of perfume, pHadjusting agent, pH buffer and preservative and which is substantiallyfree from a surfactant and a bleach to the water of the wash cycle andto the water of the rinse cycle of the clothes washing machine, whereinthe water-softening composition is added into the fabric softeningdispensing drawer of the clothes washing machine from where it issubsequently provided to the water of the rinse cycle of the clotheswashing machine, and wherein incrustations and/or watermarks left onsurfaces of the clothes washing machine and optionally fabrics isreduced.
 2. A method as claimed in claim 1, wherein the water-softeningagent is water-soluble and is selected from the group consisting ofpolycarboxylate polymers; monomeric polycarboxylates; heptonates;glucoheptonates; gluconates; oxydisuccinates; glycerol mono- di- andtrisuccinates; carboxymethyloxysuccinates; carboxymethyloxymalonates;dipicolinates; hydroxyethyliminodiacetates; phosphonates;iminodisuccinates; polyaspartic acids; butylated hydroxy toluene (BHT);and phosphonate stabilisers.
 3. A method as claimed in claim 1, whereinthe water-softening agent is within a liquid composition.
 4. A methodaccording to claim 1, wherein the acidic water-softening compositionconsists of: (a) 5 to 10% by weight of at least one water-softeningagent, (b) 40 to 90% by weight water, and (c) up to 15% by weight of atleast one ingredient selected from the group consisting of perfume, pHadjusting agent, pH buffer and preservative.
 5. A method as claimed inclaim 1, wherein the polycarboxylate polymers are selected from thegroup consisting of polyacrylates, acrylic/maleic copolymers, andacrylic phosphonates.
 6. A method as claimed in claim 1, wherein themonomeric polycarboxylates are citrates.
 7. A method according to claim1, wherein the acidic water-softening composition consists of: (a) 5 to20% by weight of at least one water-softening agent, (b) 40 to 90% byweight water, and (c) up to 20% by weight of at least one ingredientselected from the group consisting of perfume, pH adjusting agent, pHbuffer and preservative.
 8. A method according to claim 1 wherein theacidic water-softening composition is a multi-region tablet.
 9. A methodof reducing the shrinkage of fabric after the wash of the fabric in aclothes washing machine, comprising adding to the water in the washcycle and to the water in the rinse cycle of the clothes washing machinean acidic water softening composition consisting of (a) 5 to 90% byweight of at least one water-softening agent, (b) 0 to 90% by weightwater, and (c) up to 20% by weight of at least one ingredient selectedfrom the group consisting of perfume, pH adjusting agent, pH buffer andpreservative which is a liquid or a solid selected from a powder,granulate or tablet and which is free from a surfactant and a bleach,and wherein incrustations and/or watermarks left on surfaces of theclothes washing machine and optionally fabrics is reduced.
 10. A methodof reducing shrinkage as claimed in claim 9 which method is applied tonatural fabrics selected from the group consisting of cotton, wool andsilk.
 11. A method according to claim 9 wherein the acidicwater-softening composition is a multi-region tablet.
 12. A method ofreducing the amount of wrinkles present in a fabric after a wash of thefabric in a clothes washing machine comprising adding to the water inthe wash cycle and to the water in the rinse cycle of the clotheswashing machine an acidic water-softening composition consisting of (a)5 to 90% by weight of at least one water-softening agent, (b) 0 to 90%by weight water, and (c) up to 20% by weight of at least one ingredientselected from the group consisting of perfume, pH adjusting agent, pHbuffer and preservative which is a liquid or a solid selected from apowder, granulate or tablet and which is free from a surfactant and ableach, further wherein incrustations and/or watermarks left on surfacesof the clothes washing machine and optionally fabrics is reduced.
 13. Amethod according to claim 12 wherein the acidic water-softeningcomposition is a multi-region tablet.